Time to SARS-CoV-2 clearance in African, Caucasian, and Asian ethnic groups

Abstract

Background: COVID-19 may become a seasonal disease. SARS-CoV-2 active circulation coupled with vaccination efforts has undoubtedly modified the virus dynamic. It is therefore important investigate SARS-CoV-2 dynamic in different groups of population following the course of spatiotemporal variance and immunization.

Methods: To investigate SARS-CoV-2 clearance in different ethnic groups and the impact of immunization, we recruited 777 SARS-CoV-2-positive patients (570 Africans, 156 Caucasians, and 51 Asians). Participants were followed and regularly tested for 2 months until they had two negative tests.

Results: The vaccination rate was 64.6%. African individuals were less symptomatic (2%), Caucasians (41%) and Asians (36.6%). On average, viral clearance occurred after 10.5 days. Viral load at diagnosis was inversely correlated with viral clearance (p < 0.0001). The time of SARS-CoV-2 clearance was higher in Africans and Caucasians than in Asians (Dunn's test p < 0.0001 and p < 0.05, respectively). On average, viral clearance occurred within 9.5 days during the second semester (higher rate of vaccination and SARS-CoV-2 exposition), whereas it took 13.6 days during the first semester (lower rate of vaccination and SARS-CoV-2 exposition) (Mann-Whitney t-test p < 0.0001).

Conclusion: In conclusion, ethnicity and spatiotemporal changes including SARS-CoV-2 exposition and immunization affect SARS-CoV-2 clearance.

Keywords: COVID‐19; RT‐PCR; SARS‐CoV‐2 clearance; ethnicity; herd immunity; vaccination.

FIGURE 1

(A) Analysis of variance: Ct values at diagnosis significantly differed between the ethnical groups (ANOVA, Kruskal–Wallis test p < 0.0001). It was lower in unvaccinated in Semester 1 (S1) versus unvaccinated in Semester 2 (S2) (Dunn's test p < 0.0001). Ct values at diagnosis of unvaccinated individuals during S2 were significantly higher than vaccinated individuals during S1 and S2 (Dunn's test p < 0.0001). Also, Ct values of unvaccinated individuals during S1 were significantly higher than vaccinated individuals during S1 and S2 (Dunn's test p < 0.0001). (B,C) Linear regression and correlation: (B) time to viral clearance based on age and (C) ORFab Ct values based on age. The observation was not significant (NS).

FIGURE 2

Linear regression and correlation between time to viral clearance and ORFab Ct values. (A) All participants: a significant inversed correlation between ORFab Ct values at diagnosis and time to viral clearance (slope = −0.43, r = −0.29, p < 0.0001) was observed. (B) Black African population: the inversed correlation between ORFab Ct values at diagnosis and time to viral clearance was significant (slope = −0.44, r = −0.3, p < 0.0001). (C) Caucasian population: inversed correlation between ORFab Ct values at diagnosis and time to viral clearance is significant (slope = −0.42, r = −0.35, p < 0.0001) was significant. (D) Asian population: no significant correlation was observed (slope = −0.19, r = −0.16, p: not significant [NS]).

FIGURE 3

Longitudinal measures of ORFab Ct values in Africans, Caucasians, and Asians: (A) all participants (vaccinated and unvaccinated). At diagnosis and a week after, ORFab Ct values were significantly lower in Africans compared with Caucasians (two‐way ANOVA, multiples comparisons test; diagnosis p < 0.001; Day 7 p < 0.0001). (B) Only vaccinated participants. At diagnosis and at Day 7, ORFab Ct values were significantly lower in in Africans compared with Caucasians and Asians (Africans vs. Caucasians p < 0.001; Africans vs. Asians p < 0.0001).

FIGURE 4

(A) The time to viral clearance significantly differed between the ethnical groups (ANOVA, Kruskal–Wallis test p < 0.0001). It was higher in Africans versus Caucasians (Dunn's test p < 0.01) and Asians (Dunn's test p < 0.0001). The time to viral clearance was also higher in Caucasians versus Asians (Dunn's test p < 0.05). (B) After correction for unvaccinated: no differences in time to viral clearance between Black Africans and Caucasians. The time to viral clearance of Africans and Caucasians remained significantly higher than that of Asians (Dunn's test p < 0.0001 and p < 0.05, respectively).

FIGURE 5

Effect of vaccines and group immunity on time to viral clearance. (A) Semester 1 (S1: lower vaccination rate and low SARS‐CoV‐2 exposition): no significant difference between vaccinated and non‐vaccinated individuals. (B) Semester 2 (S2: higher vaccination rate and high SARS‐CoV‐2 exposition [87%]): time to viral clearance decreased significantly (ANOVA, Kruskal–Wallis test p < 0.0001). The time to viral clearance of S2‐non‐vaccinated individuals was significantly lower than that of S1‐non‐vaccinated individuals (Dunn's post‐test p < 0.0001). Also, the time to viral clearance of S2‐vaccinated individuals was significantly lower than that of S1‐vaccinated individuals (Dunn's post‐test p < 0.05).